Shape optimization of Extended Tube Muffler using Threshold Acceptance, Simulated Annealing and FEM Methods

A numerical assessment of single expansion-chamber muffler with extended tube under limited space is performed by the maximisation of the sound transmission loss (STL) using the Transfer Matrix Method (TMM) and Finite Element Method (FEM). This shape optimization analysis is performed using Threshold Acceptance (TA) and Simulated Annealing (SA) schemes , the STL's maximization with respect to a one-tone noise is introduced, the best designs obtained by the two methods are compared and analysed by Finite Element Method (FEM). The Transfer Matrix Method (TMM) and the FEM solution are used to analyse the STL of the shape optimized mufflers, a standard computational code COMSOL Multiphysics is used to analyse in 3D the sound attenuation of the muffler by the FE method. The acoustical ability of the muffler obtained is than assessed by comparing the FEM solution with the analytical method. Results show that the best acoustical performance is obtained with TA optimizer and the maximal STL is precisely located at the desired targeted tone. Consequently, the optimal approach on the design of single expansion-chamber muffler with extended tube presented in this study provides quick and novel schemes for the shape optimization of muffler under limited space.